The present invention relates to a clamping device for a cutting insert, in particular, for an insert for the turning of grooves and parting.
Cutting inserts, for example, for grooving and parting are clamped in holders of the blade type in order to achieve narrow widths of cut. Further, the term "blade type" also includes slitting cutters and circular saw blades.
U.S. Pat. No. 4,801,224 describes a clamping device for a cutting insert in a holder of the blade type, including a cutting insert which can be clamped in a slot in the blade. The cutting insert is clamped by the spring action which is created by deflection of a clamping finger which is an integral part of the holder. In order to press the cutting insert into its correct position in the slot, a special installation tool is used which consists of a rod with two pins in the one end surface. Admitted, this device functions satisfactorily but it nevertheless suffers from certain drawbacks. For example, the cutting insert itself forces the spring clamp finger upwards each time a cutting insert is mounted, causing a certain wear of the contact surfaces of the clamping finger which works against the cutting insert and which, over an extended period, damages the contact surface such that the cutting insert no longer sits with the same stability which it had at the beginning and therefore, the entire blade holder must be exchanged.
Also in U.S. Pat. No. 4,588,333 a clamping device in a blade holder is described, according to which the cutting insert is clamped in a slot by spring action which is created by the deflection of a clamping finger which is integrated into the blade holder. According to this design, the cutting insert is pressed into the insert pocket by the operator by pushing the end surface of a hard rod or bar against the front part of the cutting insert. In a manner similar to that in U.S. Pat. No. 4,801,224 the cutting insert is then prized out by applying one of the two pins on the rod behind the cutting insert and levering it out. Even with this design, the contact surface of the holder which acts against the cutting insert, wears each time a cutting insert is inserted or extracted. Further, even in this case, there is the inconvenience that the installation tool requires space.
European Publication 0 259 847 described a blade holder with a slot for receiving the cutting insert, with an additional slot for the mounting of a clamping screw, which when activated forces the blade part between the two slots and then presses against the cutting insert, whereby the insert is clamped. Certain wear occurs when installing the cutting insert into and removing the cutting insert from the slot in which the insert is to sit. This can cause a disadvantage of the clamping screw by limiting the amount of play and inadequate distribution of clamping force.
German Document No. 33 19 799 describes a design for the clamping of a cutting insert in a blade holder wherein a clamping screw including a roller part presses with increasing radius against a round rod which, in turn, presses against the cutting insert. The design is complicated and does not provide for torque acting inwards into the insert pock to lock the cutting insert firmly with distinct abutment against the rear abutment surface in the slot which receives the insert.
It is, therefore an object of the present invention is to avoid wear of the holder abutment surfaces which work against the cutting insert.
A further object of the present invention is to maintain a large clamping force for the cutting insert during an extended period of time.
Another object of the invention is to attain the most exact positioning of the cutting insert possible when clamping, with distinct abutment against a rear abutment surface in the slot which receives the insert.